I'm going in another direction from this race to the bottom. My total weight is 80 pounds. That includes my bike and everything on it, except me. Including food, water, my helmet and bike shoes. The panniers alone weigh almost 9 pounds. Believe it or not, despite everybody posting here, my setup is no heavier than the average cyclotourist. I meet many carrying more than me.My observation has been that U/L tourists are the small minority on the road. I have found backpacking the same way. I read about a lot of folks that go U/L, but see very few of them out on the road or trail. After having read a lot about U/L I was surprised by this. I know that on the road I am often mistaken for a credit card tourist and when backpacking I am enough of an oddity that people always comment on my little backpack and ask what I have in it.
I'm not sure you'd want to cross the Mojave Desert with an ultralight load. I carried 24 pounds of water.
I really don't see the amount of water I need to carry as being a factor in how minimal I go with the rest of my gear. I have done a good bit of riding in the desert with both light and ultralight setups. I find that I can generally find a route where I don't need more than 24 hours of riding without access to a water source and that is typically only for a single day here and there. Sometimes lack of water resupply might mean a longer than I would have preferred day.
In one case I went so far as to carry what must have been close to a gallon of water bottles in my jersey pockets. In another case I used a tiny lightweight backpack to carry water for a long dry day. For those few days I pick up used sport drink or bottled water bottles.
I guess that there are places where you could go for multiple days without water resupply, but yeah, I will skip those.